1. Field of the Invention
This invention relates to security devices and more particularly to an adjustable bar lock for a sliding window or door.
2. Description of the Prior Art
Slidable members that are movable along a path between an open and a closed location in sliding doors and windows are normally equipped with a locking device; but many standard locking devices are easy to force open despite being locked. In order to insure safety, numerous devices have been developed which maintain the slidable member in a closed location.
In particular, bar locks which extend longitudinally in the path of movement of the slidable member have been extensively employed both as primary security devices and as backups to locking devices provided with sliding doors and windows. Such bar locks offer several advantages. First of all, they are typically placed in compression when resisting an opening force applied to the slidable member, and hence tend to be relatively strong and capable of withstanding a substantial force. Secondly, a positive interface between the slidable member and an abutment member is effected. Further advantages of such bar locks lie in their relative simplicity of operation and manufacture. A person can generally tell at a glance whether a sliding door or window is locked depending upon the absence or presence of a bar lock in the path of movement of the slidable member. The presence of a bar lock may also serve to discourage an intruder from attempting passage through a respective sliding window or door.
The simplest bar locks comprise merely elongated members, for example thick wooden dowels or pipes, wedged between a slidable member and an abutment member. However, such devices are generally cut to fit only a particular size of sliding window or door, and do not include mechanisms for conveniently retaining them out of the way in their respective pass positions.
Another type of bar lock is exemplified by the Harris U.S. Pat. No. 3,615,114 which shows a locking apparatus comprising an inner bar and an outer bar telescopically connected. The outer ends of such bars respectively abut an abutment member and a slidable member. When the slidable member is in its closed location, the locking apparatus is placed between the slidable member and the abutment member, thereby locking the slidable member in the closed location. The Harris apparatus may be shortened and left in the path of the slidable member, thereby allowing only partial freedom of movement of the slidable member; or it may be shortened and removed completely from the path of the slidable member, but is then susceptible to being lost or misplaced. A disadvantage with this device is that no provision is made for retaining it in a pass position.
The Means U.S. Pat. No. 3,698,754 discloses a device which is locked in place by using an overcenter pivot. The device comprises a telescopic member and a rigid member connected by the overcenter pivot. The respective ends of the telescopic and rigid members are pivotally attached to the slidable and abutment members. The overcenter pivot allows the telescopic and rigid member to collapse in a vertical plane, substantially out of the path of the moveable slidable member. However, these links will be prevented from collapsing in a scissors-like manner to a position substantially parallel with each other unless they are approximately the same length. Thus, if the length of the adjustable link is altered, the shorter link will prevent the longer link from rotating to a vertical position to allow the door to completely open.
Therefore, prior devices tended to restrict the operation of sliding windows and doors, to be relatively complex in structure and manufacture or to lack adjustability and provisions for securing them in an out of the way position.